The present invention relates to a device and method of managing the life of a toner cartridge as well as an image-forming apparatus using the same.
An image forming apparatus which forms an image through use of toner must manage the life of a toner cartridge by ascertaining the amount of toner consumption or the amount of remaining toner in order to facilitate maintenance, such as toner replenishment, or preservation of image quality. Japanese Patent Publication No. 2002-174929A discloses a method for calculating toner consumption with simple configuration which enable accurate determination of toner consumption.
A relationship between the number of a printed dot and the amount of toner consumption is nonlinear, and the relationship also changes depending on the state of another printed dot adjacent to that printed dot. In light of this relationship, the method classifies a train of printed dots into three patterns; that is, an isolated dot, two consecutive dots, and an dot of intermediate value. The number of dots formed is counted on a per-pattern basis. The amount of toner consumption is determined on the basis of the counted values.
In such an image forming apparatus, the toner filled in the toner cartridge is gradually consumed and decreased as a result of repeated formation of an image. When the amount of toner filled in the cartridge has decreased to a certain level or less, a message “Please replace the toner cartridge” appears on a display of the image forming apparatus, thereby alerting the user.
Even in view of effective utilization of resources, the user desires to accurately recognize the amount of toner consumption and replace a toner cartridge at an appropriate time. This publication teaches a pattern into which a train of printed dots is arranged is classified into three categories. There is disclosed determination of the amount of toner consumed per page during a certain job period on the basis of the pattern in which a train of printed dots is arranged. However, there is no description on the configuration for knowing the residual amount of toner contained in the toner cartridge and judging the point of time for the interchange of the toner cartridge.
Japanese Patent Publication No. 2001-83846A discloses a technique for individually displaying the residual amounts of toner for a large-capacity cartridge and a small-capacity cartridge. Specifically, there are provided a gauge used for displaying the residual amount of toner corresponding to the large-capacity cartridge and a gauge used for displaying the residual amount of toner corresponding to the small-capacity cartridge. In this case, the residual amounts of toner are displayed as absolute values (analog values). For this reason, the user can judge the current values of the residual amounts of toner visually.
However, there is a problem that the cost of the mechanism for individually displaying the residual amounts of toner increases. Moreover, the residual amount of toner in the small-capacity cartridge is displayed at a reduced ratio compared with the residual amount of toner in the large-capacity cartridge or displayed with a color different from the color used for displaying the residual amount of toner in the large-capacity cartridge. Or the two display forms are different, for example, in the width of change of each gauge. There is a problem that the user has a difficulty in reading the displayed residual amounts of toner.